Plese make sure ld knows where to look for the Informix libs:
ldd /usr/lib/php/modules/informix.so

This is the ldd result:

linux-gate.so.1 =>  (0x00a24000)
libifsql.so => /opt/informix/lib/esql/libifsql.so 0x00cbe000)
libifasf.so => /opt/informix/lib/libifasf.so (0x0098e000)
libifgen.so => /opt/informix/lib/esql/libifgen.so (0x00faa000)
libthcli.so => /opt/informix/lib/esql/libthcli.so (0x00d86000)
libifos.so => /opt/informix/lib/esql/libifos.so (0x00196000)
libifgls.so => /opt/informix/lib/esql/libifgls.so (0x00c7a000)
libdl.so.2 => /lib/libdl.so.2 (0x00aed000)
libcrypt.so.1 => /lib/libcrypt.so.1 (0x0072a000)
libifglx.so => /opt/informix/lib/esql/libifglx.so (0x00a67000)
libc.so.6 => /lib/libc.so.6 (0x003e9000)
libpthread.so.0 => /lib/libpthread.so.0 (0x00164000)
libm.so.6 => /lib/libm.so.6 (0x00111000)
/lib/ld-linux.so.2 (0x009ce000)


Actually libifos.so is in /opt/informix/lib/esql directory

My installed Informix csdk version is:

csdk-2.90.UC4-1


Thanks

And `ldconfig -p | grep informix`, please.

This is the `ldconfig -p | grep informix` result:


libtxbsa.so (libc6) => /opt/informix/lib/libtxbsa.so
libtxa.so (libc6) => /opt/informix/lib/esql/libtxa.so
libtsql.so (libc6) => /opt/informix/lib/esql/libtsql.so
libtos.so (libc6) => /opt/informix/lib/esql/libtos.so
libthxa.so (libc6) => /opt/informix/lib/esql/libthxa.so
libthsql.so (libc6) => /opt/informix/lib/esql/libthsql.so
libthos.so (libc6) => /opt/informix/lib/esql/libthos.so
libthgen.so (libc6) => /opt/informix/lib/esql/libthgen.so
libthasf.so (libc6) => /opt/informix/lib/libthasf.so
libtgen.so (libc6) => /opt/informix/lib/esql/libtgen.so
libtasf.so (libc6) => /opt/informix/lib/libtasf.so
libnetstub.so (libc6) => /opt/informix/lib/libnetstub.so
libixxa.so (libc6) => /opt/informix/lib/esql/libixxa.so
libixsql.so (libc6) => /opt/informix/lib/esql/libixsql.so
libixos.so (libc6) => /opt/informix/lib/esql/libixos.so
libixglx.so (libc6) => /opt/informix/lib/esql/libixglx.so
libixgls.so (libc6) => /opt/informix/lib/esql/libixgls.so
libixgen.so (libc6) => /opt/informix/lib/esql/libixgen.so
libixfgisql.so (libc6) => /opt/informix/lib/esql/libixfgisql.so
libixcobsql.so (libc6) => /opt/informix/lib/esql/libixcobsql.so
libixasf.so (libc6) => /opt/informix/lib/libixasf.so
libifxa.so (libc6) => /opt/informix/lib/esql/libifxa.so
libifsql.so (libc6) => /opt/informix/lib/esql/libifsql.so
libifos.so (libc6) => /opt/informix/lib/esql/libifos.so
libifglx.so (libc6) => /opt/informix/lib/esql/libifglx.so
libifgls.so (libc6) => /opt/informix/lib/esql/libifgls.so
libifgen.so (libc6) => /opt/informix/lib/esql/libifgen.so
libiffgisql.so (libc6) => /opt/informix/lib/esql/libiffgisql.so
libifcss.so (libc6) => /opt/informix/lib/libifcss.so
libifcobsql.so (libc6) => /opt/informix/lib/esql/libifcobsql.so
libifasf.so (libc6) => /opt/informix/lib/libifasf.so
libdb2tsql.so (libc6) => /opt/informix/lib/esql/libdb2tsql.so
libdb2thsql.so (libc6) => /opt/informix/lib/esql/libdb2thsql.so
libdb2thgen.so (libc6) => /opt/informix/lib/esql/libdb2thgen.so
libdb2tgen.so (libc6) => /opt/informix/lib/esql/libdb2tgen.so
libdb2ixsql.so (libc6) => /opt/informix/lib/esql/libdb2ixsql.so
libdb2ixgen.so (libc6) => /opt/informix/lib/esql/libdb2ixgen.so
libdb2ifsql.so (libc6) => /opt/informix/lib/esql/libdb2ifsql.so
libdb2ifgen.so (libc6) => /opt/informix/lib/esql/libdb2ifgen.so
libbsa.so (libc6) => /opt/informix/lib/libbsa.so



Thanks for your concern

Cannot reproduce.

Well, a friend of mine called Alonso 'Teletubbie' Vallejo has invented this trick for me:

1) In /opt/informix/lib/esql did:

nm -A libifos.so | grep ifx_checkAPI

result:
-------
libifos.so:         U ifx_checkAPI

It seems like the symbol is not defined there because of the "U" character preceeding it.


2) Searching in /opt/informix/esql/cli he found:

nm -A libthcli.so | grep ifx_checkAPI

result:
-------
libthcli.so:0009c5d8 T ifx_checkAPI

It seems like the symbol is defined there.  OK he copies the libthcli.so file to /opt/informix/lib/esql

3)He ran ./configure and trick the generated Makefile like this:

INFORMIX_SHARED_LIBADD = -Wl,-rpath,/opt/informix/lib/esql -L/opt/informix/lib/esql -Wl,-rpath,/opt/informix/lib -L/opt/informix/lib -lifsql -lifasf -lifgen -thcli -lifos -lifgls -ldl -lcrypt -lifglx

(regard the -thcli included to link the file)

4)Then he ran make, and copies the informix.so to /usr/lib/php/modules

And !voil?!

I don't know if this was the right way but my PHP connection to Informix is working fine right now.  

Thanks.



5)Copi

The "U" means "undefined", this symbol is defined in checkapi.o, which is compiled in the extension itself during the build.
If it's not, then you must be doing something terribly wrong.

But I only follow the recommended steps as i described in my first message, I am pretty sure about that.  Informix esql library was extracted directly from Informix RPMS.  OK I did not build PHP from sources again, but build the informix.so module used to be enough for previous releases (5.1.x over FC3).  I am concern now about next releases, probably it will be so hard to get an Informix environment again.

Thanks.